In Vitro Antimicrobial Activity of Mouthrinse Containing Amine-Stannous Fluoride

Objectives: To evaluate the in vitro antimicrobial activity of a commercial mouthrinse containing amine fluoride and stannous fluoride (AmF/SnF2) as active ingredients. Methods: 20 bacterial species were selected for evaluation. The test product (AmF/SnF2) was compared with a positive control (0.2% chlorhexidine-CHX) and a negative control (saline). Each strain was processed independently. The strains were recovered by subculturing, and a bacterial solution was prepared in sterile saline and inoculated into 10 mL of each tested product, with a contact time of exactly 1 minute, and 1mL of the contact solution was inactivated by diluting it in 9 mL of a universal dilution agent with lecithin. Then, serial ten-fold dilutions were carried out and a 20 minute period of neutralization was allowed for the dilutions. Each bacterial strain was then incubated under the proper conditions. From the total counts, the colony forming units (CFU) after contact with the tested products and the percentage of bacterial survival, relative to the negative control (saline), were calculated. Comparisons were tested using the Kruskal-Wallis and the Sign Tests. Results: Significant differences in the bacterial counts were detected (p<0.001). These differences were identified among the three products compared by paired test: CHX versus saline (p<0.001), AmF/SnF2 versus saline (p<0.001), and CHX versus AmF/SnF2 (p=0.001).Only one bacterial species showed higher than 10% or survival against the mouth rinse containing AmF/SnF2 (A. naeslundii). For the CHX product, nine bacterial species demonstrated resistance: low levels of resistance (10-50% of survival) were detected of S. mutans, S. sanguis and S. salivarius, P. anaerobius and L. casei; and a very limited effect (>50% of survival) were observed for A. actinomycetemcomitans, A. naeslundii, M. micros, V. parvula. Conclusion: Within the limitations of this in vitro test, significant differences were detected in antimicrobial activity among AmF/SnF2 and the positive and negative controls.